tsc -w get compiles its own output again

[jrieken]

TypeScript Version:

1.8.10

Code

{
    "compilerOptions": {
        "module": "commonjs",
        "target": "ES6",
        "noLib": true,
        "outDir": "out"
    },
    "exclude": [
        "node_modules"
    ]
}

Have a file extension.js and run once tsc -p jsconfig.json which gives you a file out/extension.js. Start tsc in watch mode, make a change to extension.js

Expected behavior:

The compiler should auto-magically exclude the outDir.

Actual behavior:

It recurses forever which make the terminal print funny patterns

[basarat]

The compiler should auto-magically exclude the outDir.

QQ if someone already knows: What is the current behavior of

// foo.ts
console.log('hello');

With allowJs + no outDir. Is foo.js automagically excluded? 🌹

[mhegazy]

outDir is excluded by default if you do not specify "exclude" (node_modules behave similarly). the rational was, if we always include it, there is no way for you to disable this. with the current approach, you can not specify "exclude", and get the automatic behavior or specify one, and disable the automatic behavior.

[jrieken]

@mhegazy So when exactly is the endless recursion a desired behaviour?

[mhegazy]

When you put it this way, the answer is never :)

the issue was, if we always added, some one will have a request to undo that, and there will be no way of doing this, unless we add a new flag --noImplicitOutDirExclusion (which is something we would rather not do). that is the same argument for node_modules as well.

[jrieken]

I understand that and I think it's a fair decision, tho I think it would be better if the compiler eventually stops. Like not be triggered by a file it emitted in the previous round

[mhegazy]

One thing we can do, is include it by default, and then let users override that using the include property (from #5980)

[basarat]

I've gone with : outDir is always excluded for alm

Feeding the the output of the compiler back to the input of the same compiler seems wrong. And outDir is I guess the recommended way to support allowJS alm-tools/alm#75 🌹